Many optical systems require precision optomechanical mountings that hold optical elements in the positions and orientations required for operation of the system. To achieve proper positioning and alignment of an optical element, an optomechanical mounting generally must allow movement or rotation of the optical element relative to other optical elements during an alignment process, but once the optical element is aligned the mounting must securely hold the optical element to maintain the proper alignment during shipping and use of the optical system.
Friction plays an important, but competing role in both the alignment and the securing of the optical elements. During alignment, the force of friction is desirably comparatively low, allowing ease of motion of parts. After the elements are aligned, friction is desirably comparatively high, providing reliability of the device or structure.